Interannual Variation in the Zooplankton Community of the North Adriatic Sea under Short-Term Climatic Anomalies

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Zooplankton played an important role in the regulating the material circulation and energy flow in marine ecosystem. The climate change has been considered as a major factor to affect the structure of zooplankton community. This manuscript studied the possible effect of short-term climatic anomalies on the zooplankton community in North Adriatic Sea. The results were very interesting. The manuscript will provide a key support for understanding the evolution of marine ecosystem in the future resulted from the climate change. I suggested that this manuscript should be accepted after minor revision. The specific comments were as follows:

 Line 13 Please change “of” into “in”.

 Figure 1 The y-axis should be added a solid line.

Figure: The typeface in the figures should be changed into Time New Romman.

If possible, English expression needed to be further corrected, especially grammar.

Comments on the Quality of English Language

If possible, English expression needed to be further corrected, especially grammar..

Author Response

Reviewer 1

Zooplankton played an important role in the regulating the material circulation and energy flow in marine ecosystem. The climate change has been considered as a major factor to affect the structure of zooplankton community. This manuscript studied the possible effect of short-term climatic anomalies on the zooplankton community in North Adriatic Sea. The results were very interesting. The manuscript will provide a key support for understanding the evolution of marine ecosystem in the future resulted from the climate change. I suggested that this manuscript should be accepted after minor revision. The specific comments were as follows:

Line 13 Please change “of” into “in”.

Author’s answer: The sentence was changed according to Reviewer’s suggestion.

Figure 1 The y-axis should be added a solid line.

Author’s answer: Figure 1 was modified according to Reviewer’s suggestion.

Figure: The typeface in the figures should be changed into Time New Romman.

Author’s answer: The typeface of all figure has been updated to Times New Roman.

If possible, English expression needed to be further corrected, especially grammar.

Author’s answer: The whole paper was thoroughly checked for errors to improve grammar and readability.

Reviewer 2 Report

Comments and Suggestions for Authors

This work presents the differences between the zooplankton communities in the N Adriatic Sea in two separate summers, and the role of environmental variables and climate change in shaping the changes observed. The manuscript is well written, and the methods and results are clearly described. However, a description of what is the typical zooplankton community composition in the region is missing, and information on this respect needs to be included in the Introduction (Study area) and referred to in the Discussion. The differences between June 2019 and 2022 are obvious, but it is not clear if 2019 reflects the usual zooplankton structure in previous years or not. For example, are there usually Noctiluca and doliolids blooms in June? Or it happened in 2019 because it was a rainy year? Could it be that the changes observed reflect a change in phenology? Have the authors considered that perhaps the lower fluorescence and higher copepod abundance observed in 2022 might be due to an advancement in time of the zooplankton bloom due to the increasing temperatures, rather than a reduced productivity? Please note that the fluorescence recorded is not a proxy of primary production but of the chlorophyll/phytoplankton biomass standing stock at the time of sampling. Therefore, the predators might be blooming during the 2022 cruise, after having already consumed the protists bloom.

Specific comments:

- Line 119-120, please write in full MAdDW and SAdDW.

- Line 151,426, please amend, fluorescence is a proxy for biomass not for production rates.

- Which factors could be driving the differences between station 48 and the rest? And between years at the same st. 48? No explanation is given in the Discussion.

- Pseudodiaptomus marinus, usually presents low numbers by day and higher abundance at night. Were all stations sampled by day? Please specify in Methods.

- Figure 6, please amend legend, delete 'relative' as data are presented as ind/m2 and not as %.

- Line 454, please consider changing 'algae' by 'protist', since Noctiluca is described as heterotrophic.

 

 

Author Response

Reviewer 2

This work presents the differences between the zooplankton communities in the N Adriatic Sea in two separate summers, and the role of environmental variables and climate change in shaping the changes observed. The manuscript is well written, and the methods and results are clearly described. However, a description of what is the typical zooplankton community composition in the region is missing, and information on this respect needs to be included in the Introduction (Study area) and referred to in the Discussion. The differences between June 2019 and 2022 are obvious, but it is not clear if 2019 reflects the usual zooplankton structure in previous years or not. For example, are there usually Noctiluca and doliolids blooms in June? Or it happened in 2019 because it was a rainy year? Could it be that the changes observed reflect a change in phenology? Have the authors considered that perhaps the lower fluorescence and higher copepod abundance observed in 2022 might be due to an advancement in time of the zooplankton bloom due to the increasing temperatures, rather than a reduced productivity? Please note that the fluorescence recorded is not a proxy of primary production but of the chlorophyll/phytoplankton biomass standing stock at the time of sampling. Therefore, the predators might be blooming during the 2022 cruise, after having already consumed the protists bloom.

Author’s answer: We thank the reviewer for the helpful suggestions and insights provided.

Data on the June community for the study area have been added in the study area section and referenced in the discussion. Noctiluca appears to be a common blooming species in the Adriatic, especially in late spring- early summer. Doliolids were also previously found in high numbers in the month of June.

The possibility of a change in plankton phenology to justify the reduction in chlorophyll a was scrutinized, finding that even before the survey the levels of chlorophyll concentration were extremely low. However, the possibility of a shift in zooplankton phenology was pointed out in the discussion, expressing the need of a large timescale study.

 

Specific comments:

- Line 119-120, please write in full MAdDW and SAdDW.

Author’s answer: The full name for both abbreviations was added in the study area section.

- Line 151,426, please amend, fluorescence is a proxy for biomass not for production rates.

Author’s answer: Both sections were changed from production to phytoplankton biomass.

- Which factors could be driving the differences between station 48 and the rest? And between years at the same st. 48? No explanation is given in the Discussion.

Author’s answer: The possible explanation was added in the Discussion. Station 48 is the most southern and shallowest one, characterized by the highest temperature and the lowest oxygen concentration. These extreme conditions might be the cause for the lower level of similarity registered in the cluster analysis. Finally, fluorescence was much lower in 2022 in the same station, which might explain the interannual differences in local community composition.

- Pseudodiaptomus marinus, usually presents low numbers by day and higher abundance at night. Were all stations sampled by day? Please specify in Methods.

Author’s answer: More details about the sampling strategy were specified in Methods.

- Figure 6, please amend legend, delete 'relative' as data are presented as ind/m2 and not as %.

Author’s answer: The figure was modified according to reviewer’s suggestion.

- Line 454, please consider changing 'algae' by 'protist', since Noctiluca is described as heterotrophic.

Author’s answer: The line was changed according to reviewer’s suggestion.